IDC's newest survey of server vendors shows boxes running every kind of operating system -- except Unix -- sold more during the last three months of 2010. Sales of Linux servers rose 29 percent; Windows rose 16.8 percent, but most surprisingly, sales of mainframes shot up 69 percent â€" the highest growth rate IDC ever found on mainframes.

"Linux isn't Unix, it is rather a written-from-scratch independent implementation...

Yes Linux was written from scratch, so is Solaris or AIX or HP-UX or even *BSD. All of them are Unix! "

No, Solaris or AIX or HP-UX and even *BSD were not written from scratch. They all inherited an existing codebase that came before them, they are all "forks" of an earlier version of Unix. They are all Unix.

Only Linux, and the original Unix itself, were written from scratch.

Linux is not Unix. There is not one line of Unix source code in Linux. Linux was written from scratch, by Linus Torvalds.

In this figure, solid lines entering from the left represent existing source code.

Do you understand now?

PS: BTW, the GNU/Linux OS uses GNU (and GNU was written from scratch, by Richard Stallman), but the Linux kernel itself does not use GNU, so the Linux kernel was also written from scratch. Android uses the Linux kernel, but it does not use GNU AFAIK.

GNU is also not Unix. In fact, the very abbreviation, GNU, satnds for GNU is Not Unix.

http://en.wikipedia.org/wiki/GNU"GNU is a recursive acronym for "GNU's Not Unix!", chosen because GNU's design is Unix-like, but differs from Unix by being free software and containing no Unix code."

Yes Linux was written from scratch, so is Solaris or AIX or HP-UX or even *BSD. All of them are Unix!

Linux is not Unix. Period.
It's not based on Unix code, it's not Unix certified. It's not Unix.
AIX, HP-UX and BSD all share a common heritage which Linux does not.
In fact, Linux wasn't even intended to be a Unix clone. Originally it was a Minix clone (which also is not Unix).

So anyone who tells you that Linux is any way related to Unix (beyond architecture similarities) is simply WRONG.

The design principles Tanenbaum applied to MINIX greatly influenced the design decisions Linus Torvalds applied in the creation of the Linux kernel. Torvalds used and appreciated MINIX, but his design deviated from the MINIX architecture in significant ways, most notably by employing a monolithic kernel instead of a microkernel. This was famously disapproved of by Tanenbaum in the Tanenbaumâ€“Torvalds debate.

Linux is a clean-room clone of Minix. There was never any UNIX code in Linux. It's is the bastard step-child of UNIX' distant cousin Minix. No actual blood relation; no actual code history.

BSD is a continuation of AT&T UNIX source code, with a bunch of extra features added in. By the year 1992, there was no original AT&T UNIX code in BSD anymore, but the history is still there, and you can trace back through the CVS commit logs back to the original UNIX sources.

While none of the free implementations of BSD have paid the exorbitant fees to go through the certification process and thus none can call themselves UNIX(tm), they are most definitely Unix-based systems.

MacOS X is a crazy hibrid of NeXT, FreeBSD, NetBSD, and Mach, giving it direct links into the UNIX source code lineage. And, Apple has paid for specific versions to go through the certification process. Thus, it is also UNIX(tm).

But there is no way, no how, none possible, for Linux to be considered UNIX(tm), or even Unix-based, or even Unix-compatible.